1. Field of the Invention
The present invention relates to a projection type video display including an LED array composed of a plurality of LEDs as a light source.
2. Description of the Background Art
Nowadays, a light source composed of light emitting diodes (hereinafter, referred to as “LEDs”) is being used in place of a conventional lamp light source in a projection type video display. In particular, in a digital light processing (DLP, registered trademark) video display that includes a digital micromirror device (DMD), LEDs emitting red light, LEDs emitting green light, and LEDs emitting blue light are used, and the LEDs of three colors are sequentially turned on (for example, see Japanese Patent Application Laid-Open No. 2005-331705). One example of such a projection type video display includes an LED array composed of a plurality of LEDs as a light source for higher brightness. Hereinbelow, an LED array emitting red light is referred to as an R-LED array, an LED array emitting green light is referred to as a G-LED array, and an LED array emitting blue light is referred to as a B-LED array. In the above-mentioned projection type video display, a drive circuit is provided for every LEDs constituting an LED array or every a plurality of groups. Specifically, for example, an R-LED array is composed of six LEDs and a drive circuit is provided for every three groups each of which is composed of two LEDs.
In the above-mentioned video display, input video signals are converted into pieces of digital data of respective colors, that is, into red data (hereinbelow, referred to as “R data”), green data (hereinbelow, referred to as “G data”), and blue data (hereinbelow, referred to as “B data”), and the DMD is driven in accordance with the pieces of data of respective colors, whereby light beams of three colors are subjected to intensity modulation. That is, the red light is subjected to intensity modulation in accordance with the R data, the green light is subjected to intensity modulation in accordance with the G data, and the blue light is subjected to intensity modulation in accordance with the B data. The light beams of three colors subjected to intensity modulation are projected onto, for example, a screen through light combining means and a projection lens, so that a video image appears.
In a case where, for example, one LED in the R-LED array fails and cannot turn on in the above-mentioned video display, the drive circuit of the LED that has failed stops driving the LED. In this case, the chromaticity and brightness of a video image to be projected onto a screen change upon a reduction in brightness of red. In particular, in a multivision projection type video display formed through the combination of a plurality of projection type video displays, changes in chromaticity and brightness of a video image projected by a projection type video display may impair uniformity and unity among a plurality of screens.